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In 1904, scientists described a ghastly tapeworm pulled from the bowels of a kakapo.

The revolting parasite, named Stringopotaenia psittacea, was described from a single specimen and hasn't been seen again since the host bird was de-wormed.

Professor Hamish Spencer says the species' fate was almost certainly that which kakapo are now gravely threatened with: extinction.

Yet, it's only in recent times that scientists like the Otago University evolutionary geneticist have argued that we need to be saving these disgusting creatures along with the cuddly animals they cling to.

Professor Spencer said while there were many interesting insights that parasites could tell scientists about their host species, the bigger incentive for not exterminating them could be explained by the so-called "hygiene hypothesis".

"One of the explanations for increased auto-immune problems in humans, including asthma and eczema, arise from the fact that we live in too clean an environment, where, as youngsters, our immune systems are not challenged enough and don't develop properly," he said.

"Today, there's increasing evidence that this is true."

In a new study, published in the major journal Trends in Ecology and Evolution, he and US evolutionary biologist Professor Marlene Zuk argue the same concept should apply to conservation.

He told the Herald one ironic example could be releasing an endangered species into the wild, where it could face a tougher time surviving because it had been raised in a parasite-free environment and didn't have a resistant enough immune system to face those parasites it encountered.

"So we should be preserving their parasites for the host's sake as well," he said.

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"A lot of people have already pointed out that we can't just preserve the cute and cuddly, we've got to preserve the ugly as well; conservation is not just about protecting biodiversity but also the processes that generate it."

He expected that, worldwide, there were thousands of cases like the kakapo tapeworm, where species had been affected by misguided but well-intentioned eradications.

In the study, the researchers note that zoos and other captive animal facilities generally have extensive anti-parasite procedures, and when animals are reared they are not inoculated with a standard assortment of parasitic organisms.

"Perhaps more worryingly, protocols of reintroduction programmes often require the very opposite, with animals dosed with a range of anti-parasitic treatments before release," they wrote.

Professor Spencer said while they were not calling for conservation managers to completely ignore parasites - major parasite infestations obviously needed to be treated - retaining "low levels" of a variety of parasite infections could even improve conservation efforts.